Heat transfer system for a liquid bath



g- 23, 1965 A. A. FENNELL 3,267,993

HEAT TRANSFER SYSTEM FOR A LIQUID BATH Filed Jan. 8, 1964 F CONTROLLER Y L, 5 ii jii E1 RELAY h United States Patent v 3,267,933 HEAT TRANSFER SYSTEM FOR A LIQUID BATH Anthony A. Fennell, Fennell Corp., 379 E. Sibley Blvd., Harvey, Ill. Filed Jan. 8, 1954, S81. No. 336,526 2 Claims. (Cl. 165-26) This invention relates generally to the art of thermal controls and more particularly to means for controlling the temperature of a liquid bath.

Baths of molten salts or low melting point metals are commonly used in the heat treating of higher melting metals and alloys. One well known scheme for heating such a bath involves immersing part of a deflected tube in the bath and directing a burner flame into one end of the tube. In this system, cooling can be achieved by terminating the flow of fuel to the burner and by forcing air through the burner and thence through the tube. However, the pressure drop across the burner is sufficiently great to require fans or air pumps of appreciable capacity, and therefore substantial cost, in order to achieve a satisfactory flow of air through the tube.

Therefore, a general object of the present invention is to provide a new and improved heat transfer system for a liquid bath.

Another object of the invention is to provide heat transfer system of the submersed tube type which system is characterized by low resistance to the flow of coolant.

Yet another object of the invention is to provide a heat transfer system which is economical to install and use.

A further object of the invention is to provide a heat transfer system which is arranged to eliminate the need for high capacity pumping means for alternately employed coolant fluid.

These and other objects and features of the invention will become more apparent from a consideration of the following descriptions.

A heat transfer system in accord with the invention includes a tubular heat transfer member and a burner arrangement. The tubular heat transfer member is made up of both a lower portion which is adapted to be submersed in a liquid bath and an upper portion. The burner arrangement is disposed in the upper portion of the tubular heat transfer member and is aligned axially thereof for delivering heat to the lower portion. The heat transfer system of the invention additionally includes coolant means in the upper portion of the tubular member; and these coolant means are disposed separate from the burner arrangement for delivering a coolant fluid to the lower portion of the tubular heat transfer member.

The invention, both to its construction and mode of operation, will be better understood by reference to the following disclosure and drawing forming a part thereof, wherein:

FIG. 1 is a schematic side elevational view of a liquid bath and a heat transfer system therefor in compliance with the invention;

FIG. 2 is an enlarged side elevational view, largely in cross-section, showing the organization of the tubular heat transfer member, the burner arrangement and the coolant means employed in the heat transfer system of FIG. 1;

FIG. 3 is a somewhat enlarged plan View of the heat transfer system of FIG. 1 With the controls removed; and

FIG. 4 is an end elevational view showing the heat transfer system and liquid bath of FIG. 1 with the controls removed.

Referring now in detail to the drawing, specifically to FIG. 1, a liquid bath designated by the numeral is seen to be provided with a heat transfer system indicated 3,257,993 Patented August 23, 1966 "ice generally by the numeral 12. The liquid bath 10 includes an imperforate tank 14 which contains a suitable quantity of a heat transfer medium 16. The tank 14 may be fabricated from a suitable refractory and may be lined or unlined as is desired. Ordinarily, the heat transfer medium 16 will comprise a low melting point salt although it may also comprise a metal or eutectic mixture of metals having a suitable melting point.

The bath 10 may be used for heat treating metal parts, for example; and the parts to be so treated will be immersed in the heat transfer medium 16- after the same has been liquefied. In order to heat and thereafter control the temperature of the medium 16, the system 12 includes a tubular heat transfer member 18; and the tubular member 18 comprises a generally horizontal lower portion 20 which is adapted to be submersed in the medium 16. The tubular member 18 also comprises a deflected or generally vertically disposed upper portion 22 which rises above the level of the medium 16 and preferably above the edge of tank 14. A cap 24 closes the upper end of portion 22 and serves as the base housing for a burner unit 26. A suitable fuel is conducted from a supply 28 to the burner unit 2 6 through a conduit 30, and combustion air is delivered from a supply 32 through a conduit 34. As is illustrated in FIG. 2, the burner unit 26 includes a tubular muzzle 36 which is aligned coaxially with the upper portion 22 of the heat transfer member 18, muzzle 36 directing the flame or products of combustion through the upper portion 2 2 and into the lower portion 20 of the tubular heat transfer member. In order to exhaust the combustion gases from the tubular member 18, the lower portion 20 thereof is configurated in a U-shape as is well shown in FIG. 3, the terminus of lower portion 20 merging into a vertical vent pipe or stack 38. Advantageously, a brace bar 40 is fixed to the stack 38 and to the upper portion 22 of tubular member 18 for adding rigidity to the resultant structure.

In compliance with the features of the invention, the muzzle 36 is spaced radially inwardly from the walls of upper portion 22 to define an annular passageway 42. The system 12 incorporates a coolant unit 44; and in the disclosed embodiment, this coolant unit includes means defining an aperture which opens radially into the passageway 42. Specifically, a flanged tube 46 is secured to the portion 22 opening radially thereof through an aperture 48 as is shown in FIG. 2. Returning to FIG. 1, inlet air is supplied from the source 32 to the flanged tube 46 through a conduit 50.

In use of the heat transfer system 12, combustion air and fuel are directed to the burner unit 26 where they are ignited; and the resultant flame and hot combustion gases are directed by the muzzle 36 into the lower portion 20 of the tubular heat transfer member 18. The heat from the flame and combustion gases is thus delivered to the heat transfer medium 16. Should it be necessary to cool the medium 16, the fuel supply to the burner unit 26 will be terminated, and coolant air will be directed through the flanged tube 46 and the aperture 48 into the upper portion 22 of the tubular heat transfer me-mber 18. This coolant air then passes through the lower portion 20 to extract heat from the medium 16. Accordingly, the temperature of the bath 10 may be easily regulated; and this regulation is achieved without a need for high capacity fans or. pumps in forcing the coolant air into and through the tubular member 18 due to the fact that a separate entrance pathway is provided for the coolant. If desired, the flow of combustion air to the burner unit 26 may be continued during the time when coolant air is directed through the system. Some moderate additional cooling results.

For facility in alternatively operating the burner unit 26 and the coolant means 44, the heat transfer system 12 is arranged to incorporate a control unit 52, as is shown in FIG. 1. The control unit 52 specifically includes a thermocouple 54 or other thermal sensor, the output of which is directed to a controller 56, controller 56 operating a master relay 58. The relay 58, in turn, is employed in directing the operation of a fuel supply valve 60 and a coolant air supply valve 62, relay 58 selectively energizing valve drive mechanism 64 and 66 respectively in this regard. If desired, the relay 58 may also be employed in operating a solenoid-type fuel shut ofi valve 68. Furthermore, a manually operated valve 70 may be interposed in the combustion air supply line 34 to terminate the flow of combustion air to the burner bination comprising: a tubular heat transfer member including a lower portion adapted to be submersed in a liquid bath and including an upper portion; burner means disposed in said upper portion aligned axially thereof for delivering heat to said lower portion, including an air inlet, a fuel inlet and a flame outlet, said flame outlet being spaced radially inwardly of the walls of said upper portion to define an annular passageway; and coolant means in said upper portion separate from said burner means for selectively delivering a coolant fluid to said lower portion, including aperture means opening into said annular passageway.

2. In a heat transfer system for a liquid bath, the combination comprising: a tubular heat transfer member including a lower portion adapted to be submersed in a liquid bath and including an upper portion; burner means disposed in said upper portion aligned axially thereof for delivering heat to said lower portion, including an air inlet, a fuel inlet and a flame outlet; coolant means in said upper portion separate from said burner means for selectively delivering a coolant fluid to said lower portion, including aperture means opening intosaid'upper portion and including a coolant air inlet; and control means for selectively operating said burner means and said coolant means, including individual valve means for said fuel inlet and said coolant .air inlet, thermosensing means disposed in thermal contact with said bath, and means for operating said valve means in compliance with the conditions sensed by said thermosensing means.

References Cited by the Examiner UNITED STATES PATENTS 2,432,942 12/1947 See et a1 126-360 2,515,618 7/1950 Wa'lleruis l26360 2,751,155 6/1956 Collat 165'22 FOREIGN PATENTS 763,296 12/1956 Great Britain.

ROBERT A. OLEARY, Primary Examiner. CHARLES SUKALO, Examiner. 

2. IN A HEAT TRANSFER SYSTEM FOR A LIQUID BATH, THE COMBINATION COMPRISING: A TUBULAR HEAT TRANSFER MEMBER INCLUDING A LOWER PORTION ADAPTED TO BE SUBMERSED IN A LIQUID BATH AND INCLUDING AN UPPER PORTION; BURNER MEANS DISPOSED IN SAID UPPER PORTION ALIGNED AXIALLY THEREOF FOR DELIVERING HEAT TO SAID LOWER PORTION, INCLUDING A AIR INLET, A FUEL INLET AND A FRAME OUTLET; COOLANT MEANS IN SAID UPPER PORTION SEPARATE FROM SAID BURNER MEANS FOR SELECTIVELY DELIVERING A COOLANT FLUID TO SAID LOWER PORTION, INCLUDING APERTURE MEANS OPENING INTO SAID UPPER PORTION AND INCLUDING A COOLANT AIR INLET; AND CONTROL MEANS FOR SELECTIVELY OPERATING SAID BURNER MEANS AND SAID COOLANT MEANS, INCLUDING INDIVIDUAL VALVE MEANS FOR SAID FUEL INLET AND SAID COOLANT AIR INLET, THERMOSENSING MEANS DISPOSED IN THERMAL CONTACT WITH SAID BATH, AND MEANS FOR OPERATING SAID VALVE MEANS IN COMPLIANCE WITH THE CONDITIONS SENSED BY SAID THERMOSENSING MEANS. 